1. Field of the Invention
The present invention is directed toward the field of high-speed data transfer, and more particularly to methods and apparatus for transferring data while minimizing the number of conductors required.
2. Art Background
In general, broadband telecommunications involves transmitting data over a wide or "broad" range of frequencies. Typically, fiber conductors or fiber optics, which transmit a broad range of frequencies, are used in broadband telecommunications applications as the preferred transmission medium. The advantage of broadband telecommunications is the ability to transmit large amount of data at high-speeds. For example, broadband telecommunications permits transmission of digital video at rates sufficient to transfer full motion video.
Broadband telecommunications applications involve switching data at high aggregate bandwidth rates. For example, telecommunications systems employing fiber optics may require switching rates as high as several giga bits per second (Gbps). Broadband telecommunications systems, like traditional digital telephony systems, employ switching equipment to effectuate transmission of data from a source, such as a wide area network, to a destination, such as an end user's home or business. This type of broadband telecommunications switching equipment involves the transfer of data, at high-speeds, within a "switching fabric." Data transfer, among components or subsystems in the switching fabric, requires operation in accordance with predetermined timing specifications or requirements. For example, transmission of data within broadband switching fabrics that support high aggregate bandwidth is measured in term of optical carrier rates. (e.g., OC-3, OC-12, OC-48 . . . OC-192). Accordingly, switching fabrics in broadband telecommunications require high-speed data transfer.
Components of a telecommunications system typically have product life cycles of up to twenty years. Unlike other types of products, shutting down service of telephones or data communications of critical networks to upgrade equipment in the telecommunications network is unacceptable. Because service cannot be delayed for an extended period of time in these types of products, certain aspects of the product are designed to support various upgrades without replacing these components for long periods of time (e.g., twenty years). For example, the backplane of a switching fabric, which may include several connectors and multiple traces, cannot be replaced without an interruption in service. Line cards or port cards plug into the backplane, and support data transfer in the switching equipment at predefined rates. Typically, when service is upgraded to increase the operating speed of the switch, the line cards are removed from the backplane, and new line cards are directly inserted into the backplane as direct replacements. Accordingly, the line cards can go through several product cycles to increase the operating speed of the switch (i.e., bandwidth of the switch) without interruption of existing service. However, the backplane must be designed for several cycles of these line cards. Accordingly, it is desirable to design a backplane for a telecommunications switching fabric that supports multiple data transfer rates through various product cycle upgrades.
Backplanes in telecommunications equipment typically include a plurality of electrical connectors. Various types of electrical connectors are well-known in the art. Currently, conductor technology provides about two hundred impedance controlled signals per two inches of vertical board space. For this connector technology, two hundred signals may be coupled to the backplane via a backplane conductor, for every two inches of printed circuit board space. Thus, there is a limitation as to the number connections that a printed circuit board component can make to the backplane. The telecommunications components for the backplane also require ground and power traces that may consume over 30 percent of the remaining connections between the component and the backplane. Therefore, it is desirable to minimize the number of conductors required to implement data transfer via a backplane.